1. Field of the Invention
The present invention relates to a method and system for manufacturing a package. More particularly, the invention relates to a method and system for manufacturing a package each having a band-like side edge portion formed by joining films together.
2. Description of the Related Art
A package of the type shaped like a pouch by superposing films one upon another and then joining their respective edge portions together (hereinafter will be referred to as package) has been widely used as a package for containing a filling material comprising ingredients of an instant food, or powder or liquid such as a seasoning.
In general, a packaging machine is configured to manufacture such packages as follows. Initially, one belt-shaped film is folded widthwise to have superposed film portions, or two belt-shaped films are superposed upon each other (superposing process).
Subsequently, the superposed film portions or superposed films are joined together over the entire width thereof at predetermined intervals in the longitudinal direction to form band-shaped joint portions (joint portion forming process). In the case where one belt-shaped film is folded widthwise, the region defined between adjacent joint portions thus formed forms a pouch having an opening along a side edge of the film. On the other hand, in the case where two belt-shaped films are superposed upon each other, the superposed films are joined together along one side edge thereof to form a band-shaped side edge portion (side edge portion forming process) and the region defined by the band-shaped side edge portion and adjacent joint portions forms a pouch portion having an opening along one side edge thereof. Such a packaging machine as the so-called vertical type packaging machine is configured to form pouch portions each having opening along one joint portion. Specifically, at least one side edge of superposed films is subjected to the side edge portion forming process while the lower one of longitudinally adjacent joint portions of the films subjected to the joint portion forming process, whereby pouch portions are formed each having the longitudinally upper joint portion opened.
In turn, a filling material to be contained in each of the packages is filled into the region defined by adjacent joint portions and the side edge portion from the opening (filling process).
Subsequently, the opening is closed by the side edge portion forming process or the joint portion forming process. In this way, packages each sealed at joint portions and side edge portion thereof are completed which contain the filling material having been filled in between the superposed films, while at the same time the packages thus completed form a package-joining belt comprising such packages joined with each other by such joint portions (package-joining belt forming step).
As required, the package-joining belt is processed in accordance with its uses. For example, it is possible that each package is individually cut off from the package-joining belt, or that package-joining belt is folded or taken up into a roll.
An easy-to-open package has been proposed which has a peripheral edge portion formed with plural elongate scars extending adjacent and substantially perpendicularly to an edge of the peripheral edge portion in a staggered arrangement for rendering the sealed package easy to open (see Japanese Patent Publication No. 2731474 for example). This easy-to-open package has been realized by forming scars on a film prior to packaging (see Japanese Patent Publication No. 2731474 noted above and Japanese Patent Laid-Open Publications Nos. HEI 3-14406 and HEI 3-32598 for example). A method of forming such scars is disclosed wherein: a processing roller comprising a metal roller and plural cutting edges formed on the periphery of the metal roller is disposed as opposed to a press roller; and the processing roller and the press roller rotate in opposite directions at equal peripheral speed while contacting each other at one point through which a film is caused to pass (see FIGS. 8 and 10 of the aforementioned Japanese Patent Publication No. 2731474).
However, before putting a film formed with scars into a packaging machine, a scar band in which scars are formed in a band-shaped region need be previously formed on the film at a position to coincide with a side edge portion or joint portion of an intended package-joining belt in accordance with the size, shape and the like of a package to be manufactured. For this reason, time is required for processing a film to be put into the packaging machine; that is the so-called lead time for manufacture is necessary. In addition, scarred films each suited to a respective one of packages to be manufactured need be prepared troublesomely.
Further, the provision of scars causes the tensile strength of the film to lower, which is one of packaging operation restricting factors. With a packaging machine configured to draw a film with a large tensile force, such as a high-speed packaging machine for example, a trouble occasionally occurs such that a film formed with scars tears during the packaging operation, which lowers the operating efficiency considerably. Particularly, in adjusting the packaging machine so that a mark printed on a film will be positioned centrally of the resulting package, the position of the mark is adjusted by utilizing the resistance of the belt-shaped film. In such a case, a film formed with scars has insufficient tensile strength for such adjustment, which makes the adjustment very difficult actually.
Although, presently, such easy-to-open packages are manufactured using scarred films solely, there has not so far been known any radical means to solve the foregoing problems essential to such scarred films as a result of study made by those skilled in the art but some studies to improve only the characteristics of film itself. The inventors of the present invention have intensively and repeatedly studied in pursuit of such radical means with their attention focused on the problems which have been half overlooked and have attained the present invention.
The present invention, which has been made under such circumstances to solve the foregoing problems, has an object to provide a method and system for manufacturing easy-to-open packages using a scar-free film.